Resistance-ring of rotors.



J. M. BARR.

RESISTANCE RING OF BOTOBS. APPLIOATIQI FILED D120. 6, 1912.

1,079,629, Patented Nov. 25, 1913.

' mmfo'c Witmwom John Mc Ba r v Gbtouwg Q srriir is PATENT orricn JOHN- MARTIN BARR; or INDIANAPOLIS, IN IANA, ASSIGNOR 'ro FAIRBANKS-MORSE ELECTRICAL MANUFACTURING COMPANY,

' POM'IION OF INDIANA,

RESISTANCE-RING OF ROTORS.

Specification of Letters Patent.

OF INDIANAPOLIS, INDIANA, A (301B,-

Patented Nov. 25, 1913.

application filed December 6, 1912. Serial No. 735,266.

To all :whom itfmay concern:

.Be it known that I, JoHN MARTIN BARR, of the city of Indianapolis, county of Marion, State of Indiana, have invented certain new and useful Improvements in Resistance-Rings of Rotors, of which the follow- I ing is afull, clear, and exact description,

tors which are used in alternating to the fact that copper oxid about the conducting bars and such aswill enable those skilled in the-art to make and use the same, reference being had to the annexed drawings, which are hereby made a part of my specification.

My invention relates to squirrel-cage rocurrent induction motors, and more particularly to those squirrel-cage rotors whose conductors bars are connected together by means of a resistance ring of high conductivity.

For many years'copper resistance rings have been cast upon the copper conductors of squirrel-cage rotors, but this practice has been in many respects unsatisfactory owing the union effected between the resistance ring and'the conducting bars of the rotors, varies in its mechanical and electrical characteristics. This was due largely to the wide differences in the quality of commercial copper, to the formation of also to the fact that air-holes, cracks and voids occurred at thepointof union between the conducting bars and the resistance rings. It is a pccularity of induction motors that any impairment in the perfection of the conductivity of the secondary elements has a tendency to aggravate itself with continued operation. No satisfactory means for ascertaining the existence of these latent defects was found. A rotor with cast end rings or even show satisfactory on test,

resistance ringsmay appear entirely satisfactory on external examination and may but after being in service a time it will then demonstrate the existence of the hidden faults. I have in this my invention discovered a facile means for examining said defects, whereby they may be corrected by suitable local treatment thereof, before the rotor having such a defective resistance ring shall have been shipped from the factory. By my invention I likewise increase the ventilating surface of said resistance rings and thereby prevent their overheating.

Though my invention consists largely in the construction and arrangement 0 parts hereinafter described and particularly pointed out in the claims, yet I do not limit my invention to the precise form or construction of parts shown or the several parts thereof, inasmuch as various alterations may be made without changing the scope of my invention. I

In the drawings Figure 1 shows a rotor having a resistance ring with my inspection groovestherein, Fig. 2 shows a cross section of a resistance ring with a partly fused conductor bar therein and shows the inspection groove extending into said conductor bar. Fig.3 shows an arrangement wherein the inspection grooves are cut into the inner periphery of the resistance ring, parallel to the conducting rods or bars and extending slightly into the same. Fig. 4 showsa cross section of a resistance ring, in the face of which is cut an inspection groove, and also a groove on the inner periphery thereof.

In the drawings 5 indicates the rotor laminae, 6 the conducting bars, 7 the ends of the conducting bars embedded in the resistance ring. These ends are notched or' purpose of grooved in divers ways for the securing a better fusion with the resistance ring metal. 9 indicates an inspection groove cut in said ring. These grooves may be of any suitable shape but we prefer to use grooves of the shapeof the letter V. These inspection grooves may be cut inzthe inner periphery of the resistance rings as well as on the outer periphery or on the face thereof. A number of these grooves may be out upon a resistance'ring as may be desired.

In Fig. 3 I show an arrangementin which there are as many inspection grooves as there are conducting bars on the rotor. These grooves extend through the inner part of the resistance ring into a portion of the conducting bars which has been fused.

The inspection grooves shown in figures of the drawing show the greatly increased radiating surface obtained by their use. This increase inradiating' surface is of great value in preventing the overheating of these rings. The inspection grooves reaching down to the point where the union of rotor bars and the ring take place, allows one to readily discover the blow-holes, cracks or other imperfections in the ringand these may thereupon be treated locally in any suitable manner to eliminate the same.

What I claim as my invention is:

1. In an electric rotor, a conducting bar, a resistance element integrally united with and making electrical connection with an end of said conductingbar; said resistance element having an opening therein to reveal the integral union of said bar and the resistanoe element.

2. In an electric rotor, a conductor, a resistance element embracing an end of said conductor and integrally united therewith and having an opening formed through said element to the embraced end of said conductor.

3. In an alternafirgseurrent rotor, conducting bars, a resistance ring, having a groove therein, cut to a point-Wvhere the bars are united with the metal'of said ring.

In an alternating current motor, conducting bars, a resistance ring, having an opening in said ring extending therein and exposing a portion of the said bars in contact with the metal of said ring.

5. An electric rotor comprising two conjointly united elements,,one of which is provided with an opening to reveal the homogeneous union of the two elements.

6. In a rotor, of the class specified, a pair of elements jointly united for interelectrical conductivity; there being a notch formed which extends through the material of each element to reveal at least a portion of the joint surfaces of the elements.

JOHN MARTIN BARR.

\Vitnesses:

THURMAN '1. HALL, WILBUR W. GARD. 

